[PATCH 1/2] parisc: add functions required by KPROBE_EVENTS

[Sven Schnelle <svens@stackframe.org>]

implement regs_get_register(), regs_get_kernel_stack_nth() and
regs_within_kernel_stack()

Signed-off-by: Sven Schnelle <svens@stackframe.org>
---
 arch/parisc/include/asm/ptrace.h | 13 ++++++++++++
 arch/parisc/kernel/ptrace.c      | 35 ++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/arch/parisc/include/asm/ptrace.h b/arch/parisc/include/asm/ptrace.h
index 9ff033d261ab..143fb2a89dd8 100644
--- a/arch/parisc/include/asm/ptrace.h
+++ b/arch/parisc/include/asm/ptrace.h
@@ -37,4 +37,17 @@ extern int regs_query_register_offset(const char *name);
 extern const char *regs_query_register_name(unsigned int offset);
 #define MAX_REG_OFFSET (offsetof(struct pt_regs, ipsw))
 
+#define kernel_stack_pointer(regs) ((regs)->gr[30])
+
+static inline unsigned long regs_get_register(struct pt_regs *regs,
+					      unsigned int offset)
+{
+	if (unlikely(offset > MAX_REG_OFFSET))
+		return 0;
+	return *(unsigned long *)((unsigned long)regs + offset);
+}
+
+unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n);
+int regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr);
+
 #endif
diff --git a/arch/parisc/kernel/ptrace.c b/arch/parisc/kernel/ptrace.c
index 0964c236e3e5..a3d2fb4e6dd2 100644
--- a/arch/parisc/kernel/ptrace.c
+++ b/arch/parisc/kernel/ptrace.c
@@ -789,3 +789,38 @@ const char *regs_query_register_name(unsigned int offset)
 			return roff->name;
 	return NULL;
 }
+
+/**
+ * regs_within_kernel_stack() - check the address in the stack
+ * @regs:      pt_regs which contains kernel stack pointer.
+ * @addr:      address which is checked.
+ *
+ * regs_within_kernel_stack() checks @addr is within the kernel stack page(s).
+ * If @addr is within the kernel stack, it returns true. If not, returns false.
+ */
+int regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
+{
+	return ((addr & ~(THREAD_SIZE - 1))  ==
+		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
+}
+
+/**
+ * regs_get_kernel_stack_nth() - get Nth entry of the stack
+ * @regs:	pt_regs which contains kernel stack pointer.
+ * @n:		stack entry number.
+ *
+ * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
+ * is specified by @regs. If the @n th entry is NOT in the kernel stack,
+ * this returns 0.
+ */
+unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n)
+{
+	unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+
+	addr -= n;
+
+	if (!regs_within_kernel_stack(regs, (unsigned long)addr))
+		return 0;
+
+	return *addr;
+}
-- 
2.20.1